Changing Spark Plugs – Mitsubishi 3.0 V6 24valve

If your late model Pajero, Challenger or Magna is due for it’s 100 or 200,000km service it is possible to save yourself quite a bit of dough by replacing the spark plugs yourself.

It is a reasonably straight forward job to do and can be done with a basic spanner, screwdriver and socket set. Allow yourself plenty of time though, quite a few hours will be needed to finish the job.

There are a few precautions that you need to be aware of, nothing too drastic just little things that will make the job easier for you and they are outlined below. I had actually got halfway through this job before growing a brain and realising that this information might be useful to our readers so I’m all the steps in reverse so please don’t shoot me if there is anything I have left out! I will try my best to cover everything.

OK, dust off the tools and let’s get down to it.

Important Notes to Remember.

Allways replace the spark plugs with Platinum or Iridium plugs. Yeah they cost a bit more but you do not want to be doing this job every 20,000km or so. Good deals on these can be found on EBAY

The spark plug leads will be quite difficult to remove. Try twisting the leads first, a little each way until they come loose and then pull them out.

A smear of anti-sieze compound or even a smear of engine oil on the spark plug threads will prevent the new plugs from binding up in the alloy heads and make removal easier next time.

When you remove a component sit the bolts back into the holes where they came from. Because we are dealing with a lot of bolts this will make the re-assembly so much easier. No more trying to guess which bolt went where!

A foot-long length of hose that fits over the porcelain section of the spark plug is useful for extracting the plugs once you have them loose.

If you find it necessary to remove any of the leads from the coils be sure to mark them clearly, both on the lead and it’s coil. You don’t want to find out later that you don’t know which lead goes to which coil.

The first step is to remove the air intake. Release the four clips around the air filter housing, release the throttle cable from the intake, remove the electrical connector from the air flow meter, remove the PCV hose from the intake and undo the clamp around the throttle body.

Time to remove the throttle body. Number and remove the three vacuum hoses on the top of the tb, remove the 10mm bolt holding the throttle cable and earth strap, loosen the two 12mm nuts holding the throttle cable to it’s mount and remove the cable from the tb, remove the electrical connector from the air bypass at the bottom of the tb, and then remove the four 12mm bolts holding the tb to the intake manifold. Take a note of which way the gasket sits between the two and do not remove the two coollant hoses from the bottom of the throttle body, there is enough slack in them to simply move the tb to the side out of the way.

Now to remove the wiring harness that comes across the manifold. This is self explanatory, if it’s plugged in and in the way – unplug it! Once you have all connections and harness mounts undone move the harness out of the way.

Remove the four 12mm bolts holding the bracket in place and remove the plug leads from their holder.

Remove the fuel pressure regulator vacuum hose and remove the 10mm bolt holding the electrical connection and harness bracket – this allows access to the first plug lead.

Remove the 10mm bolt holding the two connectors to the intake manifold. One thing to rememer here is that when re-assembling, the wires for these two connectors go under the black bracket in the second picture up.

Time to remove the three coils. My advice is to remove the 10mm bolts holding them down but do not remove the plug leads unless you absolutely have to. With a bit of manouvering the coils can be moved enough not to cause any problems with the leads still attached. There is also two 12mm bolts holding the fuel supply and return lines to the manifold that have to be removed. Remove the PCV hose from the manifold at this time also.

Working on the left side of the manifold, remove the brake booster vacuum supply, 10mm bolt holding another earth strap, the charcoal canister vacuum hose and the vacuum hose at the rear of the manifold. (Yeah, ok, I’m not sure where this last one goes to!)

On the same side as above, remove the two 12mm bolts from the manifold bracket and the two 12mm bolts holding the hot air intake – this has a gasket that usually falls down when the bolts are undone so be careful!

Working from the front of the car again, undo the three 12mm bolts holding the electrical connectors and bracket. Sit them back in their respective holes in the bracket once it’s removed to avoid confusion when re-assembling.

Getting there! Now remove the remaining 12mm bolts securing the manifold. Some will be hard to see but if you look in the location of the arrows they shouldn’t be too hard to find. On the front of the manifold there is two bolts that hold down a small bracket and this can be tricky to remove. A magnetized screwdriver or small magnet works wonders for removing this.

Once all the bolts are removes the manifold should be easily lifted up and out of the engine bay. If it is stuck do not force it, have a look to be sure all the bolts are removed. Be careful not to damage the gasket between the two parts of the manifold if you plan on re-using it.

And this is what things should look like. Don’t pay any attention to the timing covers being off, I was doing the timing belt at the same time on this engine. BEFORE doing anything place a rag over the intake runners of the lower manifold to avoid getting any dirt or heaven forbid, any solid object down there!

Re-assembly is the reverse of what we have just done with attention paid to the precautions I listed at the start of the article. Visually check the spark plug gap before fitting them and use the length of hose to lower them into their holes. You don’t want to find out that one plug has a closed gap after re-fitting everything!

Doing this job yourself would save you many hours in labour charges and we all know how much mechanics need to charge these days to make a living!

29 thoughts on “Changing Spark Plugs – Mitsubishi 3.0 V6 24valve”

Thanks for the how-to Craig. I need to do the plugs on our 3.5l 24v Paj and figure even if it’s a bit different I should be able to use your guide to help make sure I get all those bolts. It’s a job I haven’t done on the Paj before and haven’t been looking forward to it.

hi craig i have just got a 2001 challenger it has 260k on the clock it needs plugs do i have to replace the leeds as well it has been well looked after and had all it’s services this is my first car wish a computer (i am old shcool)i looked under the bonet for the plugs and thorght it was to mutch for me to do but your pages are very good and i wil do it thanks.
Cheers Craig

Craig,
Thanks heaps for this information. I might very well look into doing this myself as the cost the mechnick gave me is a bit outlandish. Also was wondering if you may have put this and larger pictures into a PDF that is downloadable and printable???

Hi Bill,
I honestly hadn’t thought of putting the articles into pdf format with full size pictures but it certainly is a good idea, a lot better than reading each step off a computer screen!
I will have to have a look through my external hard drive to see if I’ve saved the full size pics, I may have just re-sized them and uploaded them to the site, I’m not real sure. This will probably take me a couple of days as our desktop has decided to call it a day and the laptop takes forever just to read the contents of the hard drive. A replacement desktop is on it’s way and as soon as I can I’ll have a look and let you know what I can do.

Hi Adrian,
The engine used in the article was a 3.0 in a Triton. The procedure for your Magna is much the same (remove the top half of the intake manifold to replace the back three plugs), albeit not quite as involved as the Triton/Pajero 3.0’s. For some reason the 3.0’s changed to the coil pack setup a lot earlier than the 3.5’s.

I do not even know how I finished up here,
however I thought this put up was once great. I do
not realize who you are however definitely you are going to
a famous blogger if you happen to are not already.
Cheers!

Thanks, found this really useful in doing the plugs in our 2007 Outlander.
Do you happen to know if there is a replaceable fuel filter in the V6 Outlanders?
Ours isn’t performing that well on fuel, and from what I can tell, the filter must be in the tank (and no mention of replacing it)
I’d rather give the fuel filter a go than the o2 sensors which are damn expensive (and not throwing up any fault codes either)

dave i know on the v6 shogun an pajero over here in the uk thye fuel filter is underneath the car an has metal cannister yype deal usually close to tank towards front of car the outlander may have it situated in a similar way

craig wilson what a good clear write up bud an as someone said a good quality pdf of the info with large clear pics in would be a great idea

I have found this article extremely useful when working on my Pajero myself. Being a female, mechanics tend to quote twice as much but I’ve always worked on my own cars from a young age. Do you know of or have you done something similar to this for replacing a water pump or the gaskets? I only ask because if I’m going to be up to my elbows in oil with the engine stripped as much as this, I would like to do them at the same time. Just abit wary about going that far.

Hi Kim,
I don’t have a tutorial on changing the waterpump on a 3.5 as yet, however I do have an article on replacing the timing belt on the 3.0 which is fairly similar and the timing belt has to be removed to replace the pump so it’s pretty relevant. You can find the article here – http://autofix.com.au/blog/timing-belt-replacement-mitsubishi-30-v6

Having said that, one of the first jobs I have in the new year is timing belt, waterpump, spark plugs and rocker cover gaskets on my wife’s 3.5 NM Pajero and I will be doing a tutorial for that, sounds like you can’t wait that long though!

One other option is to download the factory workshop manual. They do lack a fair bit of detail but it may give you the confidence to get the job done. The manuals can be found here – http://www.mitsubishilinks.com/

Other than that I will be available via email off and on over Christmas/New Year if you do get stuck.

I have a 2006 ML Triton 3.5 and have spent most of the day following your instructions and changing the spark plugs. I found your images very useful and it gave me the courage to continue even when things began to get a little daunting – I lost count of how many bolts had to be removed !!! The 3.5 is very similar to the 3.0 and anyone reading this should take heart that this instructional, a gasket kit (maybe), good spark plugs, patience, and a good set of sockets is all you need.

Some other things I found handy were:
1. A skinny 12mm socket (my sidchrome one was too fat for two bolts – the front hot air intake, and one pretty much right in the middle of the manifold)
2. One of those magnets on the end of a telescopic stick for pulling out the old spark plugs or hard to reach bolts
3. a multi angle socket attachment for that difficult to reach bolt right at the back of the manifold, driver side
4. It’s better to keep all bolts on the manifold loose when it come to reassembly, then position the two bolts at the passenger side where there’s a big black bracket, and then tighten all bolts gradually … I found that these manifold bracket bolt holes didn’t line up well, so I had to go back and loosen all the top manifold bolts again – that’s a pain.

I used a 20mm dowel with a 10mm hole drilled vertically into the end to jam the end of a new spark plug into in order to lower it into the spark plug hole; you can also use this method to feel the thread start to take, and it’s easy to pull the dowel off the spark plug.

The other thing I noted was that if it was a 12mm bolt head it’s meant to hold down the manifold, 10mm ones just hold on to brackets.

Test drive complete and all good. I’m sure I could at least halve the time I did it in next time, now I know the procedure. Thanks again for your good work.

hi guys ive just recently bought a1998 3.0ltr v6 shogun lwb the guy who sold it to me said it just needs aset of plugs done that but still runing rough so ive replaced all plugs and airflow sensor meter still no better so ive bought new ht leads could this be my problem i need help please

Hi Craig, thanks for the comprehensive work. Mine is a 2004 model Triton 3.0 and is slightly different. I have taken to photographing each step of the job as memory slips backwards with advancing years. I bought you a beer as suggested but I hope it doesn’t go flat between Australia and wherever you are.
Thanks again
Tim